A normalized wavefield separation cross-correlation imaging condition for reverse time migration based on Poynting vector

Prestack reverse time migration（PSTM） is a common imaging method; however low-frequency noises reduce the structural imaging precision. Thus, the suppression of migration noises must be considered. The generation mechanism of low-frequency noises is analyzed and the up-, down-, left-, and right-going waves are separated using the Poynting vector of the acoustic wave equation. The computational complexity and memory capacitance of the proposed method are far smaller than that required when using the conventional separation algorithm of 2D Fourier transform. The normalized wavefield separation crosscorrelation imaging condition is used to suppress low-frequency noises in reverse time migration and improve the imaging precision. Numerical experiments using the Marmousi model are performed and the results show that the up-, down-, left-, and right-going waves are well separated in the continuation of the wavefield using the Poynting vector. We compared the imaging results with the conventional method, Laplacian filtering, and wavefield separation with the 2D Fourier transform. The comparison shows that the migration noises are well suppressed using the normalized wavefield separation cross-correlation imaging condition and higher precision imaging results are obtained.

Theoretical Study on Stereodynamics of Reactions of N（^2D）＋H2→NH＋H and N（^2D）＋D2→ND＋D

The vector correlations between products and reagents for the title reactions have been calculated by the quasi-classical trajectory method at a collision energy of 21.32 kJ/mol on an accurate potential energy surface of Ho et al. （J. Chem. Phys. 119, 3063 （2003））. The peaks of the product angular distribution are found to be in both backward and forward directions for the two title reactions. The product rotational angular momentum is not only aligned, but also oriented along the negative direction of y-axis. These theoretical results are in good agreement with recent experimental findings for the two title reactions. The isotopic effect is also revealed and primarily attributed to the difference of the mass factor in the two title reactions.

言简意赅,有的放矢——谈议论文论据的表达

在高中议论文的写作教学中,学生作文的语言表达＂出轨＂现象屡见不鲜,相信老师们为此肯定花了不少功夫,但结果收效甚微。学生语言的＂出轨＂现象主要表现在论据的表达上,有的偏离题意,有的似是而非,有的若即若离等等。

Investigation of Mode and Modulation Responses in Semiconductor PS-DFB Lasers:Use of a Vector-Newton Method

A numerical model for steady state analysis and analytical expressions for the AM and FM modulation responses of DFB lasers are presented.The small signal modulation responses of 3 phase shift(PS) DFB is investigated for the first time.A new method(Vector Newton method) to obtain multiple longitudinal mode of DFB lasers is used.It is demonstrated that this method is suitable for obtaining multiple solution of high nonlinear equations.Longitudinal photon density distribution and multiple longitudinal mode of 3PS DFB and simple DFB lasers are analyzed.The results show that modulation response characteristics of 3PS DFB laser is as good as that of DFB,and PS can weaken the longitudinal spatial hole burning (LHSB) effect and is in favor of single longitudinal mode operating of lasers.

説“有方”與“方”——從《由漢簡“方”與“幡”看漢代邊卒的文化學習》一文談起

漢簡中所記的“有方”與“方”是指兩種截然不同的東西。“有方”爲漢代之兵器,它是側出小枝近乎硬折向上的戟,至遲出現在西漢中後期;“幡”是指一種旗,多用於軍事;“畫方矢”未見諸史籍,漢簡僅有一見,很可能是箭矢之一種。這三者均與邊卒的日常文化學習或書寫記事無多大關係。將“有方”中的“方”理解爲書寫工具、將“幡”理解爲拭“觚”或“方”之布,將“畫方矢”理解爲在方上書寫的工具,均是不正確的。在漢代,方和觚雖均爲書寫之材料,但二者之間的差别十分明顯。

作文评语——沟通师生的桥梁

说起批改作文,很多语文教师就感到颇伤脑筋,特别是在写作文评语时,我们往往轻率为之,三言两语,以＂见红＂为原则;或者套话连篇、空洞无物;或者用写鉴定、做总结的语言,严肃而呆板,学生读起来索然无味,

Road Surface Modeling and Representation from Point Cloud Based on Fuzzy Clustering

A scheme for an automatic road surface modeling from a noisy point cloud is presented. The normal vectors of the point cloud are estimated by distance-weighted fitting of local plane. Then, an automatic recognition of the road surface from noise is performed based on the fuzzy clustering of normal vectors, with which the mean value is calculated and the projecting plane of point cloud is created to obtain the geometric model accordingly. Based on fuzzy clustering of the intensity attributed to each point, different objects on the road surface are assigned different colors for representing abundant appearances. This unsupervised method is demonstrated in the experiment and shows great effectiveness in reconstructing and rendering better road surface.

Fast direction of arrival algorithm based on vector-sensor arrays using wideband sources

An acoustic vector sensor(AVS)can capture more information than a conventional acoustic pressure sensor(APS).As a result,more output channels are required when multiple AVS are formed into arrays,making processing the data stream computationally intense.This paper proposes a new algorithm based on the propagator method for wideband coherent sources that eliminates eigen-decomposition in order to reduce the computational burden.Data from simulations and lake trials showed that the new algorithm is valid:it resolves coherent sources,breaks left/right ambiguity,and allows inter element spacing to exceed a half-wavelength.

Mathematical model of cylindrical form tolerance

Tolerance is essential for integration of CAD and CAM. Unfortunately, the meaning of tolerances in the national standard is expressed in graphical and language forms and is not adaptable for expression, processing and data transferring with computers. How to interpret its semantics is becoming a focus of relevant studies. This work based on the mathematical definition of form tolerance in ANSI Y 14.5.1 M-1994, established the mathematical model of form tolerance for cylindrical feature. First, each tolerance in the national standard was established by vector equation. Then on the foundation of toler-ance's mathematical definition theory, each tolerance zone's mathematical model was established by inequality based on degrees of feature. At last the variance area of each tolerance zone is derived. This model can interpret the semantics of form tolerance exactly and completely.

Geostrophic meridional transport in tropical Northwest Pacific based on Argo profiles

Absolute geostrophic currents in the North Pacific Ocean were calculated using P-vector method from newly gridded Argo profiling float data collected during 2004-2009. The meridional volume transport of geostrophic currents differed significantly from the classical Sverdrup balance, with differences of 10×106 -20×106 m3 /s in the interior tropical Northwest Pacific Ocean. Analyses showed that errors of wind stress estimation could not explain all of the differences. The largest differences were found in the areas immediately north and south of the bifurcation latitude of the North Equatorial Current west of the dateline, and in the recirculation area of the Kuroshio and its extension, where nonlinear eddy activities were robust. Comparison of the geostrophic meridional transport and the wind-driven Sverdrup meridional transport in a high-resolution OFES simulation showed that nonlinear effects of the ocean circulation were the most likely reason for the differences. It is therefore suggested that the linear, steady wind-driven dynamics of the Sverdrup theory cannot completely explain the meridional transport of the interior circulation of the tropical Northwest Pacific Ocean.

居延新简“出矢鍭方”考

在以往研究的基础上,对居延新简中的"出矢鍭方"进行了释读,结合时代和社会背景,通过"矢鍭"形质演变与致伤情况的分析,对该方的药物组成进行了进一步阐释;同时,下延至后世文献对"出矢鍭"法的记载,对我国早期军事医学的情况做了初步反思。指出该方作为历史中的一个残片,可对当时的边塞生活和医疗情况做些许补充。

ALGORITHM OF SAR SATELLITE ATTITUDE MEASUREMENT USING GPS AIDED BY KINEMATIC VECTOR

In this paper,in order to improve the accuracy of the Synthetic Aperture Radar (SAR) satellite attitude using Global Positioning System (GPS) wide-band carrier phase,the SAR satellite attitude kinematic vector and Kalman filter are introduced.Introducing the state variable function of GPS attitude determination algorithm in SAR satellite by means of kinematic vector and describing the observation function by the GPS wide-band carrier phase,the paper uses the Kalman filter algorithm to obtian the attitude variables of SAR satellite.Compared the simulation results of Kalman filter algorithm with the least square algorithm and explicit solution,it is indicated that the Kalman filter algorithm is the best.

Supersymmetry and Solution of Dirac Equation with Vector and Scalar Potentials

The Dirac equations with vector and scalar potentials of the Coulomb types in two and three dimensions are solved using the supersymmetric quantum mechanics method. For the system of such potentials, the analytical expressions of the matrix dements for both position and momentum operators are obtained.

Solution of Klein-Gordon Equation for Pseudo-Coulomb Potential Plus a New Ring-Shaped Potential

Under the condition of an equal mixing of vector and scalar potentials, exact solutions of bound states of theKlein-Gordon equation with pseudo-Coulomb potential plus a new ring-shaped potential are presented. Simultaneously,energy spectrum equations are also obtained. It is shown that the radial equation and angular wave functions areexpressed by confluent hypergeogetric and hypergeogetric functions respectively.

A Multiple Model Approach to Modeling Based on Fuzzy Support Vector Machines

A new multiple models(MM) approach was proposed to model complex industrial process by using Fuzzy Support Vector Machines(F -SVMs). By applying the proposed approach to a pH neutralization titration experiment, F -SVMs MM not only provides satisfactory approximation and generalization property, but also achieves superior performance to USOCPN multiple modeling method and single modeling method based on standard SVMs.

A novel current vector decomposition controller design for six-phase permanent magnet synchronous motor

The vector control algorithm based on vector space decomposition （VSD） transformation method has a more flexible control freedom, which can control the fundamental and harmonic subspace separately. To this end, a current vector decoupling control algorithm for six-phase permanent magnet synchronous motor （PMSM） is designed. Using the proposed synchronous rotating coordinate transformation matrix, the fundamental and harmonic components in d-q subspace are changed into direct current （DC） component, only using the traditional proportional integral （PI） controller can meet the non-static difference adjustment, and the controller parameter design method is given by employing intemal model principle. In addition, in order to remove the 5th and 7th harmonic components of stator current, the current PI controller parallel with resonant controller is employed in x-y subspace to realize the specific harmonic component compensation. Simulation results verify the effectiveness of current decoupling vector controller.

Generalized Dirac Equation with Vector Structural Coefficient and Its Generalized Solutions in Biquaternions Algebra

On the base of differential biquatemions algebra and theories of generalized functions the biquaternionic wave equation of general type is considered under vector representation of its structural coefficient. Its generalized decisions in the space of tempered generalized functions are constructed. The elementary twistors and twistor fields are built and their properties are investigated. Introduction. The proposed by V.P. Hamilton quatemions algebra [1] and its complex extension - biquaternions algebra are very convenient mathematical tool for the description of many physical processes. At presence these algebras have been actively used in in the work of various authors to solve a number of problems in electrodynamics, quantum mechanics, solid mechanics and field theory. The properties of these algebras are actively studied in the framework of the theory of Clifford algebras. In the papers [2, 3] the differential algebra of biquatemions has been elaborated for construction of generalized solutions of the biquaternionic wave （biwave） equations. The particular types of biwave equations were considered, which are equivalent to the systems of Maxwell and Dirac equations and their generalizations, their biquaternionic decisions also were constructed. Here the biwave equation is considered with vector structural coefficient which is biquaternionic generalization of Dirac equations. Their generalized solutions in the space of tempered distributions are defined and their properties are researched.

Vector Control Scheme of Five-Phase Induction Machines under Open-Circuit Phase Faults

Multiphase induction machine is normally controlled using rotor field oriented vector control. Under phase（s） loss, the machine currents can be optimally controlled to satisfy certain optimization criteria. In this paper, a vector control scheme to a five-phase induction machine is introduced to ensure equal phase currents and minimum torque ripples under a phase open circuit. The controller idea can be extended to any number of phases with any number of open phases. The fundamental dq components of the stator voltage are obtained using only two PI controllers for the fundamental sequence plane, as in conventional vector control of three-phase machines. Based on steady state model, a simple expression is derived to estimate the required dq voltage components of other sequence planes to ensure equal stator phase currents and minimum torque ripple. A five-phase machine is simulated using MATLAB/Simulink to ensure controller validity.

AN ELEMENTARY ANALYSIS OF PROBLEMS IN APPLICATION OF SPACE METHOD IN STRATEGIC MANAGEMENT OF ENTERPRISES

Although it is still a new and developing subject, strategic management of enterprises, the importance of which will be understood by more and more enterprises as the reform and development is deepened, will surely be applied finally. This paper expounds how to apply the Delphi method to determine the essential elements in management and to evaluate enterprises in strategic position and action evaluation (SPACE) method of strategic management of enterprises. Meanwhile, its determination and evaluation are so realistic that they describe the strategic positions at which enterprises may be in the present competitive environment, and they establish a basis for enterprises to correctly choose their strategies of development.

Vector refinement equation and subdivision schemes in Lp spaces

In this paper we will first prove that the nontrivial L p solutions of the vector refinement equation exist if and only if the corresponding subdivision scheme with a suitable initial function converges in L p without assumption of the stability of the solutions. Then we obtain a characterization of the convergence of the subdivision scheme in terms of the mask. This gives a complete answer to the existence of L p solutions of the refinement equation and the convergence of the corresponding subdivision schemes.